What does HIRDLS stand for? What satellite is the HIRDLS instrument on?

HIRDLS stands for High Resolution Dynamics Limb Sounder. HIRDLS is an instrument on the Aura satellite, one of the three EOS satellites (Terra, Aqua, and Aura). HIRDLS is a joint mission of the United States and the United Kingdom.

For what time period is HIRDLS data available in Giovanni?

HIRDLS data are available from September 1, 2004 to November 20, 2007. This corresponds to the current version of the data (see next question). HIRDLS data has been released in "blocks" -- the next version will likely be a longer time period, though the time period will still begin on September 1, 2004.

What version of HIRDLS data are currently provided in Giovanni-3?

The current version of HIRDLS data are Version 2.04.09, also known as Collection 3.

What HIRDLS data types are available?

HIRDLS data are available as atmospheric profiles (Level 2 data). This means that the data are displayed for a single point on the Earth from the Earth's surface to an altitude above that point in the atmosphere.

What HIRDLS data parameters are currently available in Giovanni-3?

HIRDLS currently has three data parameters available for analysis in Giovanni-3:

How are the data organized? What is the spatial resolution of the data?

The data are organized with all the orbit tracks (usually 15) for a given day. Vertical resolution of the data is about 1 km. Spatial resolution is between 70 and 140 km along the orbit track between profiles.

What are the current data analysis and visualization options for HIRDLS data in this Giovanni-3 instance?

All HIRDLS data are visualized as atmospheric profiles. The atmospheric concentration of the data parameter is the X-axis of the data plot, and the atmospheric pressure is the Y-axis. Note that the Y-axis is a logarithmic scale.

When an area and time period of interest are selected (see the next two questions), the Giovanni system will choose the profiles which were nearest to the selected point. The plot legend will show the times that the profiles were acquired, and the actual latitude and longitude coordinates of the profiles. The default is three (3) profiles. See the question regarding plotting preferences below for more information.

How is the area of intererest selected for Giovanni-3 HIRDLS data?

The area of interest is selected by clicking on a point on the Java map, or providing latitude and longitude coordinates. Only a single point on the globe can be selected; an area cannot be selected. The orbit tracks are for reference. If you wish to see where the orbits are on a given day before selecting an area, choose the time period first (see the next question) and click "Update Map", then choose a point for the profiles. Note that it is not necessary to use the orbit map for the day of interest to get the profiles for the selected day. The point can be chosen and then the day of interest can be chosen, and the system will retrieve profiles nearest to that point.

How is the time period of interest selected for Giovanni-3 HIRDLS data?

The time period of interest is a single day. A range of dates cannot be chosen, i.e. for averaging atmospheric profiles. To choose a day, select the year, month, and day date using the drop-down calendrical menus. If you wish to see where the Aura orbit swaths were on that, click "Update Map" after providing the date criteria.

Are there any limits on the region or time period of interest that can be selected?

There are no limits on the area that can be selected, but the data will only be for the point on the orbit nearest to the selected point. The point selected does not have to be directly on an orbit swath for the selected date. The time-period must be a single day and must be for date within the time period of the data set (the current date range is provided next to the calendrical menus). If there are no data for that day a message will indicate no data.

Are there any limits on the number of parameters that can be plotted?

Any number of parameters up to the maximum available (currently 3) can be plotted. Subsequent HIRDLS data set versions are expected to include more data parameters.

How many profiles can I plot in a single visualization?

Up to six (6) profiles can be displayed in a parameter profile plot. The option of zero (0) profiles should not be selected.

What are the various plotting preference options for HIRDLS data in Giovanni-3?

There are four plot preference options in the Giovanni-3 HIRDLS instance. They are:

Number of profiles - This option allows the selection of the number of profiles displayed in the plot. The default option is 3, the maximum is 6, and the minimum is zero.

Show Error Bars - This option designates if error bars should be shown or not shown on the plot. The default option, "Yes", displays the error bars. Select "No" to remove the error bars from the plot.

Image X Size - This option adjusts the horizontal dimension of the plot. The data values and the axis labels are not changed.

Image Y Size - This option adjusts the vertical dimension of the plot. The data values and the axis labels are not changed.

HIRDLS and MLS measure some of the same chemical species in the atmosphere, but they also measure different parameters, and they cover slightly different ranges of the atmosphere. The EOS Chem Chart (EOS Chem was the name of the Aura mission before it launched) shows the measurements made by each instrument and how they complement each other. In particular, HIRDLS measures some chlorinated fluorocarbon species (CFCs) that MLS does not measure.

Due to the obstruction of the HIRDLS scanning mirror, on the ascending (day) portion of the orbit HIRDLS is looking near the previous/earlier orbit of MLS, and on the descending (night) portion of the orbit HIRDLS is looking close to the next/later orbit of MLS. HIRDLS is also unable to view south of about 65° S (-65.0) latitude.